The invention relates to an air bag system which has multi-stage gas generating devices as well as a triggering process for such an air bag system.
Air bag systems of this type operate in several stages, in which case subsequent stages of the air bag system, which follow a primary stage, are ignited as a function of unhindered expansion possibilities of an air bag of the air bag system. For this purpose, strings, cords or similar mechanical devices are mounted at one end in the interior of the air bag on its material and are coupled at their other end with ignition devices of at least one subsequent stage. Only when a string, cord, etc., or all strings, cords or similar devices are acted upon by tension beyond their completely tensioned state, or, in other words, when the air bag can expand further beyond a defined position in an unhindered manner, will a triggering of a subsequent stage be caused, for example, by means of the string tension.
In general, the invention therefore relates to the ignition of a second or additional air bag stage as a function of the moving possibility of the surface of an air bag of an air bag system which surface advances because of the ignition of a primary stage or a generally preceding stage of the air bag system.
In particular, the invention relates to an air bag system, as it is revealed in principle in German Patent Applications 197 03 945.6, 197 09 257.8 and 197 15 463.8. Additional embodiments and characteristics of such air bag systems are disclosed in German Patent Applications 197 12 782.7, 197.26 878.1 and 197 33 896.8. All above-mentioned German patent applications are applications by the present applicant. For avoiding repetitions, the disclosure contents of all German patent applications are fully included in the present documents by this reference, specifically concerning characteristics for the multi-stage ignition or the triggering of air bag systems in the older applications.
In the above-mentioned German Patent Applications 197 03 945.6, 197 09 257.8 and 197 15 463.8, the second air bag stage is ignited in that cables on the interior side of the air bag front of the air bag system moving during the expanding of the air bag onto the occupant and unlocking, for example, a spring-prestressed striking pin and the latter strikeing onto an igniter.
The technology disclosed in the above-mentioned German patent applications relates particularly to mechanical triggerings and controls for the multi-stage ignition of air bag systems, but electrically or electronically ignitable subsequent stages are also mentioned. However, the disclosures of the above-mentioned older patent applications do not contain concrete implementations of the control of electrically or electronically ignitable subsequent stages of such air bag systems which can be ignited in several stages.
It is an object of the invention to provide a practical further development of an air bag systems which can be ignited in several stages and has at least one electrically or electronically ignitable subsequent stage, and a practical triggering process therefor.
This object is achieved by an air bag arrangement as well as which includes at least one electric switch a triggering process for such an air bag system. Advantageous further developments are contained in the respective dependent claims and their combinations.
Air bag systems of this type have several stages, in which case subsequent stages of the air bag system which follow a primary stage are ignited as a function of the unhindered expansion of an air bag of the air bag system. For this purpose, strings, cords or similar mechanical devices are mounted at one end in the interior of the air bag on its material and are coupled at their other end with ignition devices of at least one subsequent stage. Only when a string, cord, etc., or all strings, cords or similar devices are acted upon by tension beyond their completely tensioned state and tear, in other words, when the air bag can further expand unhindered beyond a certain point, a triggering of a subsequent stage is caused, for example, by the tearing-off of the string.
The invention therefore provides an air bag system which has multi-stage gas generating devices, with a primary stage for the partial inflating of an air bag and at least one subsequent stage which can be electrically and/or electronically triggered only as a function of an unhindered expansion of the air bag because of the inflating of a preceding stage, at least one electric switch being provided which can be switched as a function of the undisturbed, i.e., unhindered, expansion of the air bag because of the inflating of the preceding stage and is connected for the electric and/or electronic triggering of the subsequent stage.
Each switch is preferably coupled to the air bag by means of mechanical devices. As an alternative or in addition, it is preferred that each electric switch is formed by a tear element which is coupled to the air bag of mechanical devices. During the unimpaired (unhindered) expansion of the air bag because of the inflating of a preceding stage of the gas generating devices, this tear element is severed. These versions can be further developed in that the mechanical devices for coupling each switch or optionally each tear element to the air bag are formed by cables or strings of defined positions and lengths.
It is also preferred that, for each switch or optionally each tear element, when the air bag system is not triggered, a voltage is grounded, and when the air bag expands unhindered because of the inflating by a preceding stage of the gas generating devices, the switch opens or the tear element is severed, so that the grounding of the voltage is prevented. A further development consists of the fact that each switch or optionally each tear element is connected to the voltage source by means of a "pull-up" resistor or a terminal resistor. As an alternative or in addition, the voltage may amount to 12V.
The air bag system according to the invention can advantageously be further developed such that a plurality of electric switches is provided, and each switch is connected to an input of a common AND-circuit which is designed for emitting output signals for triggering the subsequent stage. In this case, the AND-circuit may be an AND-gate. As an alternative or in addition, the AND-circuit or optionally the AND-gate may respond to a voltage change of each switch and, in the case of a defined voltage change of all switches, emit an output signal for triggering the subsequent stage. The latter version can be further developed in that the defined voltage change is a voltage rise at all inputs of the AND-circuit or optionally of the AND-gate.
Another advantageous further development of the air bag system according to the invention consists of the fact that the at least one switch or optionally the AND-circuit or the AND-gate is coupled to a power device which is designed for the igniting of the subsequent stage as a function of a switching condition change of the at least one switch, of all switches or optionally of an output signal of the AND-circuit or of the AND-gate. The power device can preferably be constructed as a thyristor circuit or as a transistor circuit.
In the case of an air bag system according to the invention, a control unit may also be provided which, as a function of vehicle-occupant-specific data, blocks or activates the triggering of the subsequent stage or optionally the power device irrespective of a switching condition change of the at least one switch, of all switches or optionally of an output signal of the AND-circuit or of the AND-gate. This version can be further developed in that a diode is connected between, the at least one switch, all switches or optionally the AND-circuit or the AND-gate and the triggering of the subsequent stage or optionally of the power device. As an alternative or in addition, a diode can be connected between, the control unit and, hand, the power device. In this case, the two diodes can be connected in parallel and/or in the same direction.
Furthermore, the invention provides a triggering process for an air bag system with multi-stage gas generating devices, by a primary stage, an air bag being partially inflated and, only as a function of an unhindered expansion of the air bag, because of the inflating by a preceding stage, at least one subsequent stage being electrically and/or electronically triggered, in addition, as a function of the unhindered expansion of the air bag because of the inflating by the preceding stage, at least one electric switch being operated, and, as the result, the subsequent stage being electrically and/or electronically triggered.
A preferred further development of the process according to the invention consists of the step of an unhindered expansion because of the inflating by a preceding stage of the gas generating devices, with the switch operated by the severing of a tear element which is coupled to the air bag by mechanical devices.
As an alternative or in addition, in the case of the triggering process according to the invention for an air bag system as a function of the unhindered expansion of the air bag because of the inflating by the preceding stage, a plurality of electric switches can be operated and the subsequent stage can be triggered as a function of the operation of some or of all of the switches.
A further preferred embodiment of the process according to the invention consists of the fact that the triggering of a subsequent stage is blocked or activated as a function of vehicle-occupant-specific data irrespective of a switching condition change of the at least one switch.
In the following, the invention will be explained in detail by means of embodiments illustrated in the drawing in which additional characteristics and combinations of characteristics are disclosed.